1. Field Of The Invention
The present invention relates in general to television receivers which are capable of performing a picture-out-picture (referred to hereinafter as POP) mode, and more particularly to an apparatus and a method for searching an input picture in a television receiver in which a video signal inputted through a channel of the television receiver and an external input video signal can be searched together.
2. Description Of The Prior Art
Referring to FIG. 1, there is shown a block diagram of a conventional apparatus for searching an input picture in a television receiver. As shown in this drawing, the conventional input picture search apparatus comprises a first tuner 1 for detecting a broadcasting signal received through an antenna, a second tuner 2 for detecting a different broadcasting signal received through a different antenna, a first intermediate frequency processing circuit 3 for processing the broadcasting signal Va detected by the first tuner 1 at audio and video intermediate frequencies to separate audio and video signals from the broadcasting signal Va, and a second intermediate frequency processing circuit 4 for processing the broadcasting signal Vb detected by the second tuner 2 at audio and video intermediate frequencies to separate audio and video signals from the broadcasting signal Vb.
A video signal processing circuit 5 is provided in the conventional input picture search apparatus to process the video signal Vi1 from the first intermediate frequency processing circuit 3 so that it can be displayed as a main picture.
A picture-in-picture (referred to hereinafter as PIP) processing circuit 6 is also provided in the conventional input picture search apparatus to process the video signal Vi2 from the second intermediate frequency processing circuit 4 so that it can be displayed as a sub-picture.
A picture ratio converter 7 is also provided in the conventional input picture search apparatus to convert a ratio of an output video signal V1 from the video signal processing circuit 5 to an output video signal V2 from the PIP processing circuit 6 into a main picture to sub-picture ratio.
Also, the conventional input picture search apparatus comprises a color signal processing circuit 8 for displaying an output video signal V3 from the picture ratio converter 7 on a Braun tube, and a microprocessor 10 for outputting a plurality of control signals to perform a function selected by a key matrix unit 9.
The operation of the conventional input picture search apparatus with the above-mentioned construction will hereinafter be described with reference to FIGS. 1 to 3.
FIG. 2 is a view illustrating pictures displayed in a PIP mode in a general television receiver and FIG. 3 is a view illustrating pictures displayed in a POP mode in the general television receiver.
First, the broadcasting signal Va detected by the first tuner 1 is processed at the audio and video intermediate frequencies by the first intermediate frequency processing circuit 3 and the broadcasting signal Vb detected by the second tuner 2 is processed at the audio and video intermediate frequencies by the second intermediate frequency processing circuit 4. As a result, the audio and video signals Ai1 and Vi1 are outputted from the first intermediate frequency processing circuit 3 and the audio and video signals Ai2 and Vi2 are outputted from the second intermediate frequency processing circuit 4.
The video signal Vi1 from the first intermediate frequency processing circuit 3 is processed by the video signal processing circuit 5 so that it can be displayed as the main picture. As a result, the video signal processing circuit 5 outputs the resultant video signal V1 to be displayed as the main picture. The video signal Vi2 from the second intermediate frequency processing circuit 4 is processed by the PIP processing circuit 6 so that it can be displayed as the sub-picture. As a result, the PIP processing circuit 6 outputs the resultant video signal V2 to be displayed as the sub-picture.
In the case where the PIP mode or the POP mode is selected by the key matrix unit 9 under this condition, the picture ratio converter 7 converts the ratio of the video signal V1 from the video signal processing circuit 5 to the video signal V2 from the PIP processing circuit 6 into the main picture to sub-picture ratio in response to the control signal Ctl3 from the microprocessor 10. For example, if the ratio of the video signal V1 to the video signal V2 is 4:3, it may be converted into 16:9 by the picture ratio converter 7. Also, if the ratio of the video signal V1 to the video signal V2 is 16:9, it may directly be outputted by the picture ratio converter 7.
The resultant video signal V3 from the picture ratio converter 7 is processed by the color signal processing circuit 8 and then displayed on the Braun tube CRT. At this time, the video signal processed by the color signal processing circuit 8 is displayed on the Braun tube CRT in the PIP mode as shown in FIG. 2 or the POP mode as shown in FIG. 3 according to the function selected by the key matrix unit 9.
FIG. 4 is a view illustrating, in detail, pictures displayed in the POP mode in the general television receiver. The POP mode is performed to search for a program of a pre-stored channel. In the POP mode, two still sub-pictures and a moving sub-picture are displayed as shown in FIG. 4. The moving sub-picture is the picture being presently searched. The moving sub-picture will become a still sub-picture after the lapse of a predetermined time period (about one second). Then, the search is performed for input video signals of the pre-stored channel in the stored order.
However, the above-mentioned conventional input picture search apparatus has a disadvantage in that it is impossible to search for an external input video signal during searching for the video signal inputted through the channel of the television receiver. Also, if any video signal to be searched is not present, a noise component is displayed, resulting in a degradation in a picture quality.